"I've had swollen joints, knee and other surgeries all related to my arthritis," says the 36 year-old retailer. "I found that doing the yoga in a heated room relieved some of the pain. My joints seem to have become a lot more flexible and I think the exercises have built up the muscles around the joints."

Zuck isn't talking about the kind of yoga that forces your body into a pretzel. He's a fan of something called Moksha hot yoga, which was founded by a woman who suffered from painful arthritis and offers a series of 40 different postures designed to stretch, strengthen and tone the muscles.

Three-time Olympic rower Marnie McBean used Moksha hot yoga to help her work through a major back injury from the 2000 Olympics. Like McBean, Zuck found that doing the downward dog in a heated room is vastly different from doing other kinds of yoga in a room where the heat is not turned up.

"The heat loosens things up and you are able to move further into poses," says Zuck, who has tried many different kinds of yoga over the years.

He isn't the only person who has found hot yoga to help his particular medical condition. Toronto's Dorna Chee found that it helped the joint pain she suffers from as a result of lupus, an autoimmune condition.

While Chee, 40, has always practiced yoga, she became so impressed with hot yoga that she trained to become an instructor.

Toronto's Erin Moraghan is also a convert. A senior development officer for the Arthritis and Autoimmunity Research Centre (AARC), Moraghan went all the way to India, the centre of yoga, to learn about the practice of yoga postures and breathing techniques that can make such a difference to flexibility, relaxation and strength.

When she returned to her job in Toronto and heard the success that Dorna Chee had with hot yoga, Moraghan decided to create an event that would encourage people to participate in hot yoga while raising money and awareness for arthritis and autoimmune diseases.

That cross-Canada event, now in its second year, is called The Power of Movement and involves thousands of people coming together on Sunday during one-hour yoga mega-sessions designed to raise money for research and awareness of the 4.5 million Canadians living with arthritis or an autoimmune disease.

Last year's event, the world's largest public yoga event, raised $50,000.

Sign up by Saturday at www.powerofmovement.ca to join one of several events in Calgary, Edmonton, Toronto, Ottawa and London.

According to the American Yoga Association, people with arthritis can practice many yoga postures, particularly those that focus on gentle movements designed to loosen the joints and relax large muscle groups. The breathing, relaxation and meditation techniques common to all types of yoga improve respiration and help distract attention from pain.

Information for arthritis patients from Johns Hopkins Medical Centre in Baltimore, Md., includes reports that early studies confirm the value of yoga in improving joint health, physical functioning, and mental and emotional well-being. Without exercise, arthritis symptoms often lead to decreased muscle strength and less physical energy.

Yoga can also de-stress and improve confidence in people suffering with joint disease, says Erin Moraghan.

"A yoga program combined with medication and treatment has really delivered life-changing results. What we have found is that in any kind of condition in which the joints are affected, the idea is to keep moving, to retain your mobility.

"In Moksha yoga, a warm room helps to elevate the body's temperature to keep the muscles warm and limber. The challenge of yoga requires you to be present and focused, so there is also this huge component of stress relief. There is very little opportunity to think of anything else. You can completely let go."